Integrated semiconductor components, so-called MMICs (Monolithic Microwave Integrated Circuits), are often used to generate millimeter-wave signals, e.g., in radar sensors for motor vehicles, the integrated semiconductor components being encapsulated in a housing suitable for surface mounting, e.g., an eWLB housing (embedded Wafer Level Ball Grid), and being soldered onto a circuit board. Microstrips formed on the circuit board may be used to transmit the millimeter-wave signals to an antenna and to transmit the radio echoes received from the antenna to a high frequency component (MMIC) which evaluates the signals. This type of signal transmission is preferable, in particular, even if the antenna elements are formed by patch antennas on the circuit board.
On the other hand, it is also known, however, to transmit the millimeter-wave signals with the aid of so-called waveguides. These are channel-like hollow structures, the walls of which are made conductive by plating or by coating with an electrically conductive plastic, and which therefore form a resonance chamber in which certain vibrational modes of the electromagnetic waves (millimeter waves) may propagate.
When the electrically conductive wall of the waveguide is interrupted or perforated at a point, energy may be radiated out of the waveguide or radiated into this waveguide at this point. High-performance antennas may be implemented by designing hollow-conductor structures of this type in a skillful manner.
When antennas of this type are intended for use in a radar sensor, it is necessary, however, to transmit the millimeter-wave signals from the microstrip on the circuit board to the waveguide or in the opposite direction from the waveguide to the microstrip. Various transitions and coupling structures may theoretically be used for this purpose, although the structures previously known are unsuitable for use in mass production of large quantities due to their complexity.